I'm reading them in the order they were published, myself.
"The Shadow Within" and "To Dream in the City of Sorrows" may be a bit harder to find, as they're out of print, but they're worth trying to get a hold of. I'd try local book stores that have been around for a while (for example, I found both books at my local Barnes and Noble"). "The Shadow Within" reads like an Outer Limits episode in that it's very self contained. It tells the story of Anna Sheridan and the Icarus. "To Dream in the City of Sorrows" weaves in and out of the second season and fills in the gaps between Sinclair's time on Minbar from after the short lived comic series and the third season two-parter "War Without End." It also features Marcus Cole and Catherine Sakai. Both books are exellent.
I just read the first book of the Psi Corps trilogy, "Dark Genesis," which features the ancestors of Lyta Alexander, Talia Winters, and one other character (it'd be a spoiler for the book if I told you). While I haven't read the other two books, I know the second tells the story of Bester from his childhood up until his first appearance on the series, and the third covers the time of his life after the Telepath War.
I've heard that the "Leigons of Fire" trilogy is the best of the bunch. I haven't read it either, but I know it covers the time from the end of season 5 up until either "War Without End" or "Sleeping in Light."
The new trilogy is the Techno-Mage books, only one of which is out. I've picked it up, but only skimmed the first few pages as of yet. I believe it covers the time of the first season of the show.
If you're looking for a place to start, I don't think it really matters. "The Shadow Within" and "To Dream in the City of Sorrows" can be read any time after you've seen season three, and the others after the entire series. It might help to have seen Crusade before venturing into the Techno-Mage books, though, but I don't think it's nessecarry.
"Numfar, do the Dance of Joy!"
Suggestions on B5 novels? O.K. here it goes.
1.The Centauri Trilogy
2.The PSI-Corp Trilogy
3.The Techno-Mage Trilogy
4.The Shadow Within
5.Dream in the City of Sorrows
6.The short stories from Amazing Stories
and Official B5 Magazine
7.All the rest of the books
8.Do not overlook B5 Comic Book called In
"Casting Shadows" the first book of the technomage trilogy is the best B5 book I've read so far, followed very closely by "Legions of Fire, Book I" I haven't had a chance to read the others in the trilogy yet... :/ The psi-corps trilogy is good, as well, a little slower in places, but it's a good read.
My choices would be
1. The Centauri Trilogy
2. To Dream In The City Of Sorrows
3. The Shadow Within
4. First Book Of the Techno-mage trilogy followed by the next two if they stand up to the first book.
5. The Psi Corps trilogy
My first suggestion would be to say that a post about B5-related books doesn't go in a Crusade forum. I would have thought that was pretty obvious.
Moving to B5 general discussion.
<font size="-2" color="silver">"The Babylon Project was our last, best, hope for peace.
A self-contained world five miles long, located in neutral
territory. A place of commerce and diplomacy for a quarter
of a million humans and aliens. A shining beacon in space,
all alone in the night. It was the dawn of the third age of
mankind, the year the great war came upon us all. This is
the story of the last of the Babylon stations. The year is
2259: the name of the place is Babylon 5."